I bought once Waterman. Here it is.
Waterman 50 is a piston filler.
It is my first and only among my Waterman pens with this filling system.
Short transparent ink window.
Large flexible nib.
Loooooong telescopic piston.
Original warranty from the store in Milan (Italy)
Piston filler and two lever fillers - English WM 515 and WM W5 from Canada.
The question - whether there were other Watrmans pistons?